Polyolefins are a class of polymers derived from simple olefins. Known methods of making polyolefins involve the use of Ziegler-Natta polymerization catalysts. These catalysts polymerize vinyl monomers using a transition metal halide to provide an istotactic polymer.
Numerous Ziegler-Natta polymerization catalysts exist. The catalysts have different characteristics and/or lead to the production of polyolefins having diverse properties. For example, certain catalysts have high activity while other catalysts have low activity. Moreover, polyolefins made with the use of Ziegler-Natta polymerization catalysts vary in isotacticity, molecular weight distribution, impact strength, melt-flowability, rigidity, heat sealability, isotacticity, and the like. As olefin monomers are enchained in the presence of a Ziegler-Natta catalyst system, the product polymer takes on the shape and morphology of the solid components of the Ziegler-Natta catalyst system. Polymer product having a controlled and regular morphology can be more easily transported within and between reactors employed for polymer synthesis.
Ziegler-Natta catalysts having desirable spherical shape can be produced through a precipitation method employing an organic magnesium starting material. Replacement of organic magnesium with an inexpensive magnesium halide results in catalysts particles with divergent morphology and aspherical.